linux-kernel - Re: [PATCH v8 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst

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Message-ID: <20211203182500.GD16798@blackbody.suse.cz>
Date:   Fri, 3 Dec 2021 19:25:00 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Phil Auld <pauld@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [PATCH v8 5/6] cgroup/cpuset: Update description of
 cpuset.cpus.partition in cgroup-v2.rst

Hello Longman.

On Wed, Dec 01, 2021 at 08:28:09PM -0500, Waiman Long <longman@...hat.com> wrote:
> 1) The limitation that "cpuset.cpus" has to be a superset of child's
> "cpuset.cpus" has been removed as a new patch to remove that limitation will
> be added.

Superb!

> 2) The initial transition from "member" to partition root now requires that
> "cpuset.cpus" overlap with that of the parent's "cpuset.cpus" instead of
> being a superset.

That's sensible.

> For the transition back to "member", I haven't changed the current wording
> of forcing child partition roots to become "member" yet. If you think
> keeping them as invalid partition root is better, I can made that change
> too.

I wrote I was indifferent about this in a previous mail but when I think
about it now, switching to invalid root is perhaps better than switching
to member since it'd effectively mean that modifications of the parent
config propagate (permanently) also to a descendant config, which is
an undesired v1-ism.


> Please let me know what other changes you would like to see.

I hope my remarks below are just clarifications and not substantial
changes. Besides that I find your new draft good. Thanks!

> [...]

>     An invalid partition root can be reverted back to a valid one
>     if none of the validity constraints of a valid partition root
>     are violated.

s/can be/will be/ 

(I understand the intention is to make it asynchronously and
automatically, i.e. without writing into the affected descendant(s)
cpuset.partition again.)

>     Poll and inotify events are triggered whenever the state of
>     "cpuset.cpus.partition" changes.  That includes changes caused by
>     write to "cpuset.cpus.partition", cpu hotplug and other changes
>     that make the partition invalid.

-> that change validity status

(In accordance with the comment above.)


Michal

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